The objective of this proposal is to examine the efficacy of novel adeno-associated virus (AAV) variants expressing soluble FLT-1, a potent inhibitor of VEGF-mediated neovascularization and vascular permeability, to treat diabetic macular edema (DME). DME is an advanced form of diabetic retinopathy and the leading cause of blindness among working-age Americans, representing a large and growing public health problem in the United States. Vascular endothelial growth factor (VEGF) is known to play a central role in the progression of diabetic retinopathy and is a potent inducer of vascular permeability. Pharmacotherapy using anti-VEGF agents, which has shown superiority to thermal laser in large clinical trials, is emerging as a new standard of care in the treatment of DME. Although these VEGF inhibitors provide a meaningful advance over previous therapies, the need for frequent intravitreal administrations represents a major shortcoming. AAV has emerged as a proven vector for clinical applications of ocular gene therapy and represents a promising strategy for long-term, sustained delivery of proteins to the eye. Despite its success in early clinical trials, AAV tropism limits its utility for numerous applications in the eye. The developmet of AAV variants capable of efficiently transducing the entire retina following a minimally invasive intravitreal injection would enable further applications in the clinic. We are developing soluble Flt-1 (sFLT), a highly potent (~10 pM) and naturally occurring anti- angiogenic peptide that binds and inactivates VEGF. In our preliminary data, we have identified novel AAV variants that can transfect specific cell types in the retina with high efficiency and specificity following intraviteal administration. In this Phase I proposal, we will quantify levels of sFLT produced by novel AAV variants in vivo. We will also assess and quantify vascular leakage in a rat model of diabetic retinopathy. If this Phase I project demonstrates efficacy of an AAV variant expressing sFLT, these experiments will lay the groundwork for Phase II studies to further substantiate the promise of AAV variants as a treatment for DME. PUBLIC HEALTH RELEVANCE: Diabetic macular edema (DME) is the leading cause of blindness among working-age Americans and a growing public health problem in the United States. VEGF inhibitors are emerging as a new standard of care in treating DME, but require that patients have frequent injections into their eyeball over a period of several years. We propose to develop a therapeutic based on new adeno-associated virus technology that would provide for long-term delivery of anti-VEGF therapeutics in DME without the need for frequent re-injections.